Lifelong persistence of paramyxovirus Sendai-6/94 in C129 mice: detection of a latent viral RNA by hybridization with a cloned genomic cDNA probe.

C129 mice infected intracerebrally with Sendai-6/94 virus were examined periodically for the presence of viral proteins and viral RNA over a span of 423 days. On postinfection Day 15 (PID 15) an acute infection was demonstrated by increased anti-6/94 antibody titers and expression of viral proteins. More than a year later, on PIDs 373 and 423, no viral antigens were detected. Rescue of infectious virus from the mouse brains was only observable for 74 days following cocultivation of the cells on PID 15. Later, no signs of viral persistence were found at the protein level. In a further experiment, the murine tissues and cell cultures were examined for the presence of viral RNA. Virus-specific cDNA was cloned in the bacteriophage lambda system and used as a highly specific hybridization probe. Surprisingly, 6/94 viral RNA was detectable lifelong in the brain tissue of infected mice although no proteins were expressed. Murine brain cells cocultivated on PID 15 still contained viral RNA after 245 days in culture, although the expression of viral proteins was measureable for only 80 days. The results indicate a stable latency of the 6/94 virus in cell cultures and in animals at the RNA level without detectable protein expression.